DEVELOPEMENT OF AUGMENTED REALITY SYSTEM FOR MODELING OF THREE-DIMENSIONAL SCENES
Contents
1 Review of augmented reality systems
1.1 Augmented reality technology
2 Development of the problem-solving procedure
2.2 The scheme of system components interaction
INTRODUCTION
For the time being traditional window graphical interfaces controlled by keyboard and mouse begin to go out of date and to be replaced by interactive-multimedia interfaces of man-machine interaction. These interfaces do not use usual icon-based menu, but rest upon methods of interaction inherent strictly in human being (gestures, human speech). One of these types of interfaces is augmented reality which makes it possible to demonstrate new features of objects and to get new sensations from habitual real things using a standard personal computer and standard peripheral devices. That is why there is a great number of spheres where these technologies can be employed, and design in the sphere of this technology is very urgent.
One of the application domains of augmented reality are systems of 3D modeling. There are different systems, but their functions consist in restoration of 3D scene from the file and integrating it in video stream coming from web-camera. The most famous of them are ARTag and Studierstube. Creating of the systems, restoring 3D scene on the assumption of suggested marker without using any additional sources of information is less explored sphere.
The aim of this work is designing of augmented reality system conceptual model for modeling 3D scenes.
The designed system may be divided in three subsystems: pattern recognition system, two-dimensional barcode processing system and system of processing information received from the code.
This work solves following tasks:
- review of the problem state-of-the-art:
- review of the present recognition systems;
- review of the two-dimensional barcode present notation;
- review of the 3D modeling languages;
- choice of the most suitable recognition system and two-dimensional barcode for solving the tasks of this work;
- creating the conceptual model of the future system.
REVIEW OF AUGMENTED REALITY SYSTEMS
In this chapter the augmented reality technology as well as the most well-known systems in this area will be examined.
Augmented reality technology
The augmented reality to wide extent is a technology complex that enables to get additional sensations of imaginary objects usually of auxiliary-informative nature, together with sensations coming from the real world.
In a restricted sense, that is in linkage paradigm of technology and interaction interface of human and computer, the augmented reality is mostly performed as a process of combining objects of real world and objects generated by computer. Today the majority of researches in the augmented reality sphere is concentrated on using the living or interactive video, subjected to digital processing and "supplemented" by computer graphics. More serious researches include tracking the movement of real objects, recognizing of collimating marks by computer vision and constructing controlled surrounding.
Augmented reality is different from virtual reality. Its main difference is that augmented reality posts separate artificial elements in the perception of real observed world, but virtual reality constructs a new (completely imaginary) artificial world.
To combine virtual and real objects correctly one needs to know how to compute positional relationship of real objects and real scene in general correctly. Today this problem is very difficult and maybe even impossible to solve, if the real objects are not determined beforehand. That is why special objects which are present at the scene without fail and which position is computationally easy to determine are used for operating. Such objects are called markers [4].
Different objects can act in the capacity of markers. В качестве маркеров могут выступать разные объекты. But we can mark out the following groups:
- two-dimensional barcodes;
- real world objects;
- moving objects.
DEVELOPMENT OF THE PROBLEM-SOLVING PROCEDURE
After choosing the means of solving the problem we have to design the conceptual model of solving that will be represented as a diagram and implemented.
For this purpose we have to create the set of markers that will determine the 3D scene and the scheme of the development system component interaction (library for recognition two-dimensional barcodes and pattern recognition system).
Development of the marker
The marker which determines 3D scene must possess the following characteristics:
- The 3D scene must be displayed when the camera is directed at the part of the marker;
- The marker must be found in the real-time;
- By marker content the 3D scene must be built;
In the issue of the requirement analysis the marker set represented on the picture 5.1 was suggested.
This picture is diagrammatic. The structure of the marker will include Aztec-code with information about the 3D scene in the center and id-markers situated around it. Each id-marker is recognized separately and has its coordinates in the scene which determines the restoration of the whole scene by finding one of the markers. Thus finding all the markers in the focus of the camera ceases to be necessary.
Finding and recognition of Aztec-code, which is computationally difficult, will be implemented only once while loading the scene. Interactivity won`t be lost.
The only shortcoming of this model is the absence of the identification of the area occupied by Aztec-code. If the camera is focused on this area and lose all its id-markers, the scene will not be represented.
The scheme of system components interaction
After launching the system of loading new scene the recognition library Aztec-code joins in and the barcode search by target in the center is conducted.
Picture 5 . 1 – Diagrammatic depiction of the marker
After the barcode is found, the information is read from it and checked on compliance with the checksum written in the end. The attempts continue until it is read.
After reading the barcode the received information is processed and the 3D scene element array is created.
The augmented reality system is connected and the received 3D scene in compliance with id-markers is superimposed on video stream.
After this a user may freely change the position of the camera, positioning of the scene is implemented by id-markers.
SUMMARY
During the training the main two-dimensional barcode notations as well as augmented reality systems were described. Their look-and-feel, advantages and disadvantages in the network of the augmented reality system for modeling 3D scenes creation task were determined.
The most well-known augmented reality systems were analyzed. In the issue we found out that they have different directivity. Our main interest concentrates on ARToolkit series systems. These are three systems: ArToolkit, ARToolkitPlus and Studierstube. The best is Studierstube system, but it has some difficulties in case of commercial use.
The main present notations of two-dimensional barcodes were researched. As a result we found out that some barcode notations have better protection from distortions, but contain less information, and some contain more information, but have lower protection level.
The most appropriate barcode notations and augmented reality systems were chosen. As a result, we chose Aztec-code notation containing about 2 Kbyte of information and well recognized at different camera slope angle and ARToolkitPlus system which has functions necessary for solving our project tasks is of free use.
A metamodel of future software product was created. The marker scheme describing 3D scene as well as the scheme of future application main parts interaction were suggested.
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